ValueError: External ID not found in the system: web.login

2019-05-28 08:51:28,012 13 INFO pr11 werkzeug: 172.17.0.1 - - [28/May/2019 08:51:28] "GET /web/login HTTP/1.0" 500 -
2019-05-28 08:51:28,024 13 ERROR pr11 werkzeug: Error on request:
Traceback (most recent call last):
  File "/usr/local/lib/python3.5/dist-packages/werkzeug/serving.py", line 205, in run_wsgi
    execute(self.server.app)
  File "/usr/local/lib/python3.5/dist-packages/werkzeug/serving.py", line 193, in execute
    application_iter = app(environ, start_response)
  File "/mnt/odoo-source/odoo/service/wsgi_server.py", line 166, in application
    return application_unproxied(environ, start_response)
  File "/mnt/odoo-source/odoo/service/wsgi_server.py", line 154, in application_unproxied
    result = handler(environ, start_response)
  File "/mnt/odoo-source/odoo/http.py", line 1319, in __call__
    return self.dispatch(environ, start_response)
  File "/mnt/odoo-source/odoo/http.py", line 1293, in __call__
    return self.app(environ, start_wrapped)
  File "/usr/local/lib/python3.5/dist-packages/werkzeug/wsgi.py", line 599, in __call__
    return self.app(environ, start_response)
  File "/mnt/odoo-source/odoo/http.py", line 1491, in dispatch
    result = ir_http._dispatch()
  File "/mnt/odoo-source/odoo/addons/base/ir/ir_http.py", line 212, in _dispatch
    return cls._handle_exception(e)
  File "/mnt/odoo-source/odoo/addons/base/ir/ir_http.py", line 182, in _handle_exception
    return request._handle_exception(exception)
  File "/mnt/odoo-source/odoo/http.py", line 771, in _handle_exception
    return super(HttpRequest, self)._handle_exception(exception)
  File "/mnt/odoo-source/odoo/http.py", line 310, in _handle_exception
    raise pycompat.reraise(type(exception), exception, sys.exc_info()[2])
  File "/mnt/odoo-source/odoo/tools/pycompat.py", line 87, in reraise
    raise value
  File "/mnt/odoo-source/odoo/addons/base/ir/ir_http.py", line 208, in _dispatch
    result = request.dispatch()
  File "/mnt/odoo-source/odoo/http.py", line 830, in dispatch
    r = self._call_function(**self.params)
  File "/mnt/odoo-source/odoo/http.py", line 342, in _call_function
    return checked_call(self.db, *args, **kwargs)
  File "/mnt/odoo-source/odoo/service/model.py", line 97, in wrapper
    return f(dbname, *args, **kwargs)
  File "/mnt/odoo-source/odoo/http.py", line 338, in checked_call
    result.flatten()
  File "/mnt/odoo-source/odoo/http.py", line 1270, in flatten
    self.response.append(self.render())
  File "/mnt/odoo-source/odoo/http.py", line 1263, in render
    return env["ir.ui.view"].render_template(self.template, self.qcontext)
  File "/mnt/odoo-source/odoo/addons/base/ir/ir_ui_view.py", line 1211, in render_template
    return self.browse(self.get_view_id(template)).render(values, engine)
  File "/mnt/odoo-source/odoo/addons/base/ir/ir_ui_view.py", line 1118, in get_view_id
    return self.env['ir.model.data'].xmlid_to_res_id(template, raise_if_not_found=True)
  File "/mnt/odoo-source/odoo/addons/base/ir/ir_model.py", line 1358, in xmlid_to_res_id
    return self.xmlid_to_res_model_res_id(xmlid, raise_if_not_found)[1]
  File "/mnt/odoo-source/odoo/addons/base/ir/ir_model.py", line 1349, in xmlid_to_res_model_res_id
    return self.xmlid_lookup(xmlid)[1:3]
  File "<decorator-gen-21>", line 2, in xmlid_lookup

  File "/mnt/odoo-source/odoo/tools/cache.py", line 89, in lookup
    value = d[key] = self.method(*args, **kwargs)
  File "/mnt/odoo-source/odoo/addons/base/ir/ir_model.py", line 1338, in xmlid_lookup
    raise ValueError('External ID not found in the system: %s' % xmlid)
ValueError: External ID not found in the system: web.login

The error above usually means that there was another problem on database initialization. So, if you got such error in test database, just drop the database, start database creation again and pay attention on logs for errors.

If you got such error in production database, then it could be difficult to fix that. Sorry ¯ \ _ (ツ) _ / ¯